Physical layer non-line-of-sight (nlos) path discrimination using multiple frequency carriers

ABSTRACT

Disclosed are techniques for determining a line-of-sight (LOS) path between a transmitter and a wireless device. In an aspect, a wireless device receives a first reference signal on a first frequency band at a first time, receives a second reference signal on a second frequency band at a second time, compares the first time to the second time, and determines, at least based on the comparison of the first time to the second time, which of the first reference signal and/or the second reference signal followed the LOS path between the transmitter and the wireless device.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present Application for Patent claims priority under 35 U.S.C. § 119to Greek Patent Application No. 20190100032, entitled “PHYSICAL LAYERNON-LINE-OF-SIGHT PATH DISCRIMINATION USING MULTIPLE CARRIERS,” filedJan. 16, 2019, assigned to the assignee hereof, and expresslyincorporated herein by reference in its entirety.

BACKGROUND OF THE DISCLOSURE 1. Field of the Disclosure

Aspects of the disclosure relate generally to telecommunications, andmore particularly to physical layer non-line-of-sight (NLOS) pathdiscrimination using multiple frequency carriers.

2. Description of the Related Art

Wireless communication systems have developed through variousgenerations, including a first-generation analog wireless phone service(1G), a second-generation (2G) digital wireless phone service (includinginterim 2.5G networks), a third-generation (3G) high speed data,Internet-capable wireless service and a fourth-generation (4G) service(e.g., Long-Term Evolution (LTE) or WiMax). There are presently manydifferent types of wireless communication systems in use, includingcellular and personal communications service (PCS) systems. Examples ofknown cellular systems include the cellular analog advanced mobile phonesystem (AMPS), and digital cellular systems based on code divisionmultiple access (CDMA), frequency division multiple access (FDMA), timedivision multiple access (TDMA), the Global System for Mobile access(GSM) variation of TDMA, etc.

A fifth generation (5G) wireless standard, referred to as New Radio(NR), enables higher data transfer speeds, greater numbers ofconnections, and better coverage, among other improvements. The 5Gstandard, according to the Next Generation Mobile Networks Alliance, isdesigned to provide data rates of several tens of megabits per second toeach of tens of thousands of users, with 1 gigabit per second to tens ofworkers on an office floor. Several hundreds of thousands ofsimultaneous connections should be supported in order to support largewireless sensor deployments. Consequently, the spectral efficiency of 5Gmobile communications should be significantly enhanced compared to thecurrent 4G standard. Furthermore, signaling efficiencies should beenhanced and latency should be substantially reduced compared to currentstandards.

SUMMARY

The following presents a simplified summary relating to one or moreaspects disclosed herein. Thus, the following summary should not beconsidered an extensive overview relating to all contemplated aspects,nor should the following summary be considered to identify key orcritical elements relating to all contemplated aspects or to delineatethe scope associated with any particular aspect. Accordingly, thefollowing summary has the sole purpose to present certain conceptsrelating to one or more aspects relating to the mechanisms disclosedherein in a simplified form to precede the detailed descriptionpresented below.

In an aspect, a method of determining a line-of-sight (LOS) path betweena transmitter and a wireless device includes receiving, at the wirelessdevice, a first reference signal on a first frequency band at a firsttime, receiving, at the wireless device, a second reference signal on asecond frequency band at a second time, comparing, by the wirelessdevice, the first time to the second time, and determining, by thewireless device, at least based on the comparison of the first time tothe second time, which of the first reference signal and/or the secondreference signal followed the LOS path between the transmitter and thewireless device.

In an aspect, a wireless device includes a memory, at least onetransceiver, and at least one processor, wherein the at least oneprocessor is further configured to receive, from a transmitter via theat least one transceiver, a first reference signal on a first frequencyband at a first time, receive, from the transmitter via the at least onetransceiver, a second reference signal on a second frequency band at asecond time, compare the first time to the second time, and determine,at least based on the comparison of the first time to the second time,which of the first reference signal and/or the second reference signalfollowed an LOS path between the transmitter and the wireless device.

In an aspect, a wireless device includes means for receiving, from thetransmitter, a first reference signal on a first frequency band at afirst time, means for receiving, from the transmitter, a secondreference signal on a second frequency band at a second time, means forcomparing the first time to the second time, and means for determining,at least based on the comparison of the first time to the second time,which of the first reference signal and/or the second reference signalfollowed an LOS path between the transmitter and the wireless device.

In an aspect, a non-transitory computer-readable medium storingcomputer-executable instructions includes computer-executableinstructions comprising at least one instruction instructing a wirelessdevice to receive, from the transmitter, a first reference signal on afirst frequency band at a first time, at least one instructioninstructing the wireless device to receive, from the transmitter, asecond reference signal on a second frequency band at a second time, atleast one instruction instructing the wireless device to compare thefirst time to the second time, and at least one instruction instructingthe wireless device to determine, at least based on the comparison ofthe first time to the second time, which of the first reference signaland/or the second reference signal followed a line of site (LOS) pathbetween the transmitter and the wireless device.

Other objects and advantages associated with the aspects disclosedherein will be apparent to those skilled in the art based on theaccompanying drawings and detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are presented to aid in the description ofvarious aspects of the disclosure and are provided solely forillustration of the aspects and not limitation thereof.

FIG. 1 illustrates an exemplary wireless communications system,according to various aspects.

FIGS. 2A and 2B illustrate example wireless network structures,according to various aspects.

FIG. 3 is a block diagram illustrating an exemplary UE, according tovarious aspects.

FIG. 4 illustrates an exemplary wireless communications system accordingto various aspects of the disclosure.

FIG. 5 illustrates an example of timing differences between LOS and NLOSpaths, according to aspects of the disclosure.

FIG. 6 illustrates an example of differences between LOS and NLOSround-trip-times (RTTs), according to aspects of the disclosure.

FIG. 7 illustrates a method of determining an LOS path between atransmitter and a wireless device in a wireless communications network,according to aspects of the disclosure.

Elements, stages, steps, and/or actions with the same reference label indifferent drawings may correspond to one another (e.g., may be similaror identical to one another). Further, some elements in the variousdrawings may be labelled using a numeric prefix followed by analphabetic or numeric suffix. Elements with the same numeric prefix butdifferent suffixes may be different instances of the same type ofelement. The numeric prefix without any suffix is used herein toreference any element with this numeric prefix.

DETAILED DESCRIPTION

Aspects of the disclosure are provided in the following description andrelated drawings directed to various examples provided for illustrationpurposes. Alternate aspects may be devised without departing from thescope of the disclosure. Additionally, well-known elements of thedisclosure will not be described in detail or will be omitted so as notto obscure the relevant details of the disclosure.

The words “exemplary” and/or “example” are used herein to mean “servingas an example, instance, or illustration.” Any aspect described hereinas “exemplary” and/or “example” is not necessarily to be construed aspreferred or advantageous over other aspects. Likewise, the term“aspects of the disclosure” does not require that all aspects of thedisclosure include the discussed feature, advantage or mode ofoperation.

Those of skill in the art will appreciate that the information andsignals described below may be represented using any of a variety ofdifferent technologies and techniques. For example, data, instructions,commands, information, signals, bits, symbols, and chips that may bereferenced throughout the description below may be represented byvoltages, currents, electromagnetic waves, magnetic fields or particles,optical fields or particles, or any combination thereof, depending inpart on the particular application, in part on the desired design, inpart on the corresponding technology, etc.

Further, many aspects are described in terms of sequences of actions tobe performed by, for example, elements of a computing device. It will berecognized that various actions described herein can be performed byspecific circuits (e.g., application specific integrated circuits(ASICs)), by program instructions being executed by one or moreprocessors, or by a combination of both. Additionally, the sequence(s)of actions described herein can be considered to be embodied entirelywithin any form of non-transitory computer-readable storage mediumhaving stored therein a corresponding set of computer instructions that,upon execution, would cause or instruct an associated processor of adevice to perform the functionality described herein. Thus, the variousaspects of the disclosure may be embodied in a number of differentforms, all of which have been contemplated to be within the scope of theclaimed subject matter. In addition, for each of the aspects describedherein, the corresponding form of any such aspects may be describedherein as, for example, “logic configured to” perform the describedaction.

As used herein, the terms “user equipment” (UE) and “base station” arenot intended to be specific or otherwise limited to any particular RadioAccess Technology (RAT), unless otherwise noted. In general, a UE may beany wireless communication device (e.g., a mobile phone, router, tabletcomputer, laptop computer, tracking device, wearable (e.g., smartwatch,glasses, augmented reality (AR)/virtual reality (VR) headset, etc.),vehicle (e.g., automobile, motorcycle, bicycle, etc.), Internet ofThings (IoT) device, etc.) used by a user to communicate over a wirelesscommunications network. A UE may be mobile or may (e.g., at certaintimes) be stationary, and may communicate with a Radio Access Network(RAN). As used herein, the term “UE” may be referred to interchangeablyas an “access terminal” or “AT,” a “client device,” a “wireless device,”a “subscriber device,” a “subscriber terminal,” a “subscriber station,”a “user terminal” or UT, a “mobile terminal,” a “mobile station,” orvariations thereof. Generally, UEs can communicate with a core networkvia a RAN, and through the core network the UEs can be connected withexternal networks such as the Internet and with other UEs. Of course,other mechanisms of connecting to the core network and/or the Internetare also possible for the UEs, such as over wired access networks,wireless local area network (WLAN) networks (e.g., based on IEEE 802.11,etc.) and so on.

A base station may operate according to one of several RATs incommunication with UEs depending on the network in which it is deployed,and may be alternatively referred to as an access point (AP), a networknode, a NodeB, an evolved NodeB (eNB), a New Radio (NR) Node B (alsoreferred to as a gNB or gNodeB), etc. In addition, in some systems abase station may provide purely edge node signaling functions while inother systems it may provide additional control and/or networkmanagement functions. A communication link through which UEs can sendsignals to a base station is called an uplink (UL) channel (e.g., areverse traffic channel, a reverse control channel, an access channel,etc.). A communication link through which the base station can sendsignals to UEs is called a downlink (DL) or forward link channel (e.g.,a paging channel, a control channel, a broadcast channel, a forwardtraffic channel, etc.). As used herein the term traffic channel (TCH)can refer to either an UL/reverse or DL/forward traffic channel.

The term “base station” may refer to a single physicaltransmission-reception point (TRP) or to multiple physical TRPs that mayor may not be co-located. For example, where the term “base station”refers to a single physical TRP, the physical TRP may be an antenna ofthe base station corresponding to a cell of the base station. Where theterm “base station” refers to multiple co-located physical TRPs, thephysical TRPs may be an array of antennas (e.g., as in a multiple-inputmultiple-output (MIMO) system or where the base station employsbeamforming) of the base station. Where the term “base station” refersto multiple non-co-located physical TRPs, the physical TRPs may be adistributed antenna system (DAS) (a network of spatially separatedantennas connected to a common source via a transport medium) or aremote radio head (RRH) (a remote base station connected to a servingbase station). Alternatively, the non-co-located physical TRPs may bethe serving base station receiving the measurement report from the UEand a neighbor base station whose reference radio frequency (RF) signalsthe UE is measuring. Because a TRP is the point from which a basestation transmits and receives wireless signals, as used herein,references to transmission from or reception at a base station are to beunderstood as referring to a particular TRP of the base station.

An “RF signal” comprises an electromagnetic wave of a given frequencythat transports information through the space between a transmitter anda receiver. As used herein, a transmitter may transmit a single “RFsignal” or multiple “RF signals” to a receiver. However, the receivermay receive multiple “RF signals” corresponding to each transmitted RFsignal due to the propagation characteristics of RF signals throughmultipath channels. The same transmitted RF signal on different pathsbetween the transmitter and receiver may be referred to as a “multipath”RF signal.

According to various aspects, FIG. 1 illustrates an exemplary wirelesscommunications system 100. The wireless communications system 100 (whichmay also be referred to as a wireless wide area network (WWAN)) mayinclude various base stations 102 and various UEs 104. The base stations102 may include macro cell base stations (high power cellular basestations) and/or small cell base stations (low power cellular basestations). In an aspect, the macro cell base station may include eNBswhere the wireless communications system 100 corresponds to an LTEnetwork, or gNBs where the wireless communications system 100corresponds to a NR network, or a combination of both, and the smallcell base stations may include femtocells, picocells, microcells, etc.

The base stations 102 may collectively form a RAN and interface with acore network 170 (e.g., an evolved packet core (EPC) or next generationcore (NGC)) through backhaul links 122, and through the core network 170to one or more location servers 172. In addition to other functions, thebase stations 102 may perform functions that relate to one or more oftransferring user data, radio channel ciphering and deciphering,integrity protection, header compression, mobility control functions(e.g., handover, dual connectivity), inter-cell interferencecoordination, connection setup and release, load balancing, distributionfor non-access stratum (NAS) messages, NAS node selection,synchronization, RAN sharing, multimedia broadcast multicast service(MBMS), subscriber and equipment trace, RAN information management(RIM), paging, positioning, and delivery of warning messages. The basestations 102 may communicate with each other directly or indirectly(e.g., through the EPC/NGC) over backhaul links 134, which may be wiredor wireless.

The base stations 102 may wirelessly communicate with the UEs 104. Eachof the base stations 102 may provide communication coverage for arespective geographic coverage area 110. In an aspect, one or more cellsmay be supported by a base station 102 in each coverage area 110. A“cell” is a logical communication entity used for communication with abase station (e.g., over some frequency resource, referred to as acarrier frequency, component carrier, carrier, band, or the like), andmay be associated with an identifier (e.g., a physical cell identifier(PCID), a virtual cell identifier (VCID)) for distinguishing cellsoperating via the same or a different carrier frequency. In some cases,different cells may be configured according to different protocol types(e.g., machine-type communication (MTC), narrowband IoT (NB-IoT),enhanced mobile broadband (eMBB), or others) that may provide access fordifferent types of UEs. Because a cell is supported by a specific basestation, the term “cell” may refer to either or both the logicalcommunication entity and the base station that supports it, depending onthe context. In some cases, the term “cell” may also refer to ageographic coverage area of a base station (e.g., a sector), insofar asa carrier frequency can be detected and used for communication withinsome portion of geographic coverage areas 110.

While neighboring macro cell base station 102 geographic coverage areas110 may partially overlap (e.g., in a handover region), some of thegeographic coverage areas 110 may be substantially overlapped by alarger geographic coverage area 110. For example, a small cell basestation 102′ may have a coverage area 110′ that substantially overlapswith the coverage area 110 of one or more macro cell base stations 102.A network that includes both small cell and macro cell base stations maybe known as a heterogeneous network. A heterogeneous network may alsoinclude home eNBs (HeNBs), which may provide service to a restrictedgroup known as a closed subscriber group (CSG).

The communication links 120 between the base stations 102 and the UEs104 may include UL (also referred to as reverse link) transmissions froma UE 104 to a base station 102 and/or downlink (DL) (also referred to asforward link) transmissions from a base station 102 to a UE 104. Thecommunication links 120 may use MIMO antenna technology, includingspatial multiplexing, beamforming, and/or transmit diversity. Thecommunication links 120 may be through one or more carrier frequencies.Allocation of carriers may be asymmetric with respect to DL and UL(e.g., more or less carriers may be allocated for DL than for UL).

The wireless communications system 100 may further include a wirelesslocal area network (WLAN) access point (AP) 150 in communication withWLAN stations (STAs) 152 via communication links 154 in an unlicensedfrequency spectrum (e.g., 5 GHz). When communicating in an unlicensedfrequency spectrum, the WLAN STAs 152 and/or the WLAN AP 150 may performa clear channel assessment (CCA) or listen before talk (LBT) procedureprior to communicating in order to determine whether the channel isavailable.

The small cell base station 102′ may operate in a licensed and/or anunlicensed frequency spectrum. When operating in an unlicensed frequencyspectrum, the small cell base station 102′ may employ LTE or NRtechnology and use the same 5 GHz unlicensed frequency spectrum as usedby the WLAN AP 150. The small cell base station 102′, employing LTE/5Gin an unlicensed frequency spectrum, may boost coverage to and/orincrease capacity of the access network. NR in unlicensed spectrum maybe referred to as NR-U. LTE in an unlicensed spectrum may be referred toas LTE-U, licensed assisted access (LAA), or MulteFire.

The wireless communications system 100 may further include a millimeterwave (mmW) base station 180 that may operate in mmW frequencies and/ornear mmW frequencies in communication with a UE 182. Extremely highfrequency (EHF) is part of the RF in the electromagnetic spectrum. EHFhas a range of 30 GHz to 300 GHz and a wavelength between 1 millimeterand 10 millimeters. Radio waves in this band may be referred to as amillimeter wave. Near mmW may extend down to a frequency of 3 GHz with awavelength of 100 millimeters. The super high frequency (SHF) bandextends between 3 GHz and 30 GHz, also referred to as centimeter wave.Communications using the mmW/near mmW radio frequency band have highpath loss and a relatively short range. The mmW base station 180 and theUE 182 may utilize beamforming (transmit and/or receive) over a mmWcommunication link 184 to compensate for the extremely high path lossand short range. Further, it will be appreciated that in alternativeconfigurations, one or more base stations 102 may also transmit usingmmW or near mmW and beamforming. Accordingly, it will be appreciatedthat the foregoing illustrations are merely examples and should not beconstrued to limit the various aspects disclosed herein.

Transmit beamforming is a technique for focusing an RF signal in aspecific direction. Traditionally, when a network node (e.g., a basestation) broadcasts an RF signal, it broadcasts the signal in alldirections (omni-directionally). With transmit beamforming, the networknode determines where a given target device (e.g., a UE) is located(relative to the transmitting network node) and projects a strongerdownlink RF signal in that specific direction, thereby providing afaster (in terms of data rate) and stronger RF signal for the receivingdevice(s). To change the directionality of the RF signal whentransmitting, a network node can control the phase and relativeamplitude of the RF signal at each of the one or more transmitters thatare broadcasting the RF signal. For example, a network node may use anarray of antennas (referred to as a “phased array” or an “antennaarray”) that creates a beam of RF waves that can be “steered” to pointin different directions, without actually moving the antennas.Specifically, the RF current from the transmitter is fed to theindividual antennas with the correct phase relationship so that theradio waves from the separate antennas add together to increase theradiation in a desired direction, while cancelling to suppress radiationin undesired directions.

Transmit beams may be quasi-collocated, meaning that they appear to thereceiver (e.g., a UE) as having the same parameters, regardless ofwhether or not the transmitting antennas of the network node themselvesare physically collocated. In NR, there are four types ofquasi-collocation (QCL) relations. Specifically, a QCL relation of agiven type means that certain parameters about a second reference RFsignal on a second beam can be derived from information about a sourcereference RF signal on a source beam. Thus, if the source reference RFsignal is QCL Type A, the receiver can use the source reference RFsignal to estimate the Doppler shift, Doppler spread, average delay, anddelay spread of a second reference RF signal transmitted on the samechannel. If the source reference RF signal is QCL Type B, the receivercan use the source reference RF signal to estimate the Doppler shift andDoppler spread of a second reference RF signal transmitted on the samechannel. If the source reference RF signal is QCL Type C, the receivercan use the source reference RF signal to estimate the Doppler shift andaverage delay of a second reference RF signal transmitted on the samechannel. If the source reference RF signal is QCL Type D, the receivercan use the source reference RF signal to estimate the spatial receiveparameter of a second reference RF signal transmitted on the samechannel.

In receive beamforming, the receiver uses a receive beam to amplify RFsignals detected on a given channel. For example, the receiver canincrease the gain setting and/or adjust the phase setting of an array ofantennas in a particular direction to amplify (e.g., to increase thegain level of) the RF signals received from that direction. Thus, when areceiver is said to beamform in a certain direction, it means the beamgain in that direction is high relative to the beam gain along otherdirections, or the beam gain in that direction is the highest comparedto the beam gain in that direction of all other receive beams availableto the receiver. This results in a stronger received signal strength(e.g., reference signal received power (RSRP), reference signal receivedquality (RSRQ), signal-to-interference-plus-noise ratio (SINR), etc.) ofthe RF signals received from that direction.

Receive beams may be spatially related. A spatial relation means thatparameters for a transmit beam for a second reference signal can bederived from information about a receive beam for a first referencesignal. For example, a UE may use a particular receive beam to receive areference downlink reference signal (e.g., synchronization signal block(SSB)) from a base station. The UE can then form a transmit beam forsending an uplink reference signal (e.g., sounding reference signal(SRS)) to that base station based on the parameters of the receive beam.

Note that a “downlink” beam may be either a transmit beam or a receivebeam, depending on the entity forming it. For example, if a base stationis forming the downlink beam to transmit a reference signal to a UE, thedownlink beam is a transmit beam. If the UE is forming the downlinkbeam, however, it is a receive beam to receive the downlink referencesignal. Similarly, an “uplink” beam may be either a transmit beam or areceive beam, depending on the entity forming it. For example, if a basestation is forming the uplink beam, it is an uplink receive beam, and ifa UE is forming the uplink beam, it is an uplink transmit beam.

In 5G, the frequency spectrum in which wireless nodes (e.g., basestations 102/180, UEs 104/182) operate is divided into multiplefrequency ranges, FR1 (from 450 to 6000 MHz), FR2 (from 24250 to 52600MHz), FR3 (above 52600 MHz), and FR4 (between FR1 and FR2). In amulti-carrier system, such as 5G, one of the carrier frequencies isreferred to as the “primary carrier” or “anchor carrier” or “primaryserving cell” or “PCell,” and the remaining carrier frequencies arereferred to as “secondary carriers” or “secondary serving cells” or“SCells.” In carrier aggregation, the anchor carrier is the carrieroperating on the primary frequency (e.g., FR1) utilized by a UE 104/182and the cell in which the UE 104/182 either performs the initial radioresource control (RRC) connection establishment procedure or initiatesthe RRC connection re-establishment procedure. The primary carriercarries all common and UE-specific control channels, and may be acarrier in a licensed frequency (however, this is not always the case).A secondary carrier is a carrier operating on a second frequency (e.g.,FR2) that may be configured once the RRC connection is establishedbetween the UE 104 and the anchor carrier and that may be used toprovide additional radio resources. In some cases, the secondary carriermay be a carrier in an unlicensed frequency. The secondary carrier maycontain only necessary signaling information and signals, for example,those that are UE-specific may not be present in the secondary carrier,since both primary uplink and downlink carriers are typicallyUE-specific. This means that different UEs 104/182 in a cell may havedifferent downlink primary carriers. The same is true for the uplinkprimary carriers. The network is able to change the primary carrier ofany UE 104/182 at any time. This is done, for example, to balance theload on different carriers. Because a “serving cell” (whether a PCell oran SCell) corresponds to a carrier frequency/component carrier overwhich some base station is communicating, the term “cell,” “servingcell,” “component carrier,” “carrier frequency,” and the like can beused interchangeably.

For example, still referring to FIG. 1, one of the frequencies utilizedby the macro cell base stations 102 may be an anchor carrier (or“PCell”) and other frequencies utilized by the macro cell base stations102 and/or the mmW base station 180 may be secondary carriers(“SCells”). The simultaneous transmission and/or reception of multiplecarriers enables the UE 104/182 to significantly increase its datatransmission and/or reception rates. For example, two 20 MHz aggregatedcarriers in a multi-carrier system would theoretically lead to atwo-fold increase in data rate (i.e., 40 MHz), compared to that attainedby a single 20 MHz carrier.

The wireless communications system 100 may further include one or moreUEs, such as UE 190, that connects indirectly to one or morecommunication networks via one or more device-to-device (D2D)peer-to-peer (P2P) links. In the example of FIG. 1, UE 190 has a D2D P2Plink 192 with one of the UEs 104 connected to one of the base stations102 (e.g., through which UE 190 may indirectly obtain cellularconnectivity) and a D2D P2P link 194 with WLAN STA 152 connected to theWLAN AP 150 (through which UE 190 may indirectly obtain WLAN-basedInternet connectivity). In an example, the D2D P2P links 192 and 194 maybe supported with any well-known D2D RAT, such as LTE Direct (LTE-D),WiFi Direct (WiFi-D), Bluetooth®, and so on.

The wireless communications system 100 may further include a UE 164 thatmay communicate with a macro cell base station 102 over a communicationlink 120 and/or the mmW base station 180 over a mmW communication link184. For example, the macro cell base station 102 may support a PCelland one or more SCells for the UE 164 and the mmW base station 180 maysupport one or more SCells for the UE 164.

According to various aspects, FIG. 2A illustrates an example wirelessnetwork structure 200. For example, an NGC 210 (also referred to as a“5GC”) can be viewed functionally as control plane functions 214 (e.g.,UE registration, authentication, network access, gateway selection,etc.) and user plane functions 212, (e.g., UE gateway function, accessto data networks, IP routing, etc.) which operate cooperatively to formthe core network. User plane interface (NG-U) 213 and control planeinterface (NG-C) 215 connect the gNB 222 to the NGC 210 and specificallyto the control plane functions 214 and user plane functions 212. In anadditional configuration, an eNB 224 may also be connected to the NGC210 via NG-C 215 to the control plane functions 214 and NG-U 213 to userplane functions 212. Further, eNB 224 may directly communicate with gNB222 via a backhaul connection 223. In some configurations, the New RAN220 may only have one or more gNBs 222, while other configurationsinclude one or more of both eNBs 224 and gNBs 222. Either gNB 222 or eNB224 may communicate with UEs 204 (e.g., any of the UEs depicted in FIG.1). Another optional aspect may include location server 230, which maybe in communication with the NGC 210 to provide location assistance forUEs 204. The location server 230 can be implemented as a plurality ofseparate servers (e.g., physically separate servers, different softwaremodules on a single server, different software modules spread acrossmultiple physical servers, etc.), or alternately may each correspond toa single server. The location server 230 can be configured to supportone or more location services for UEs 204 that can connect to thelocation server 230 via the core network, NGC 210, and/or via theInternet (not illustrated). Further, the location server 230 may beintegrated into a component of the core network, or alternatively may beexternal to the core network.

According to various aspects, FIG. 2B illustrates another examplewireless network structure 250. For example, an NGC 260 (also referredto as a “5GC”) can be viewed functionally as control plane functions,provided by an access and mobility management function (AMF)/user planefunction (UPF) 264, and user plane functions, provided by a sessionmanagement function (SMF) 262, which operate cooperatively to form thecore network (i.e., NGC 260). User plane interface 263 and control planeinterface 265 connect the eNB 224 to the NGC 260 and specifically to SMF262 and AMF/UPF 264, respectively. In an additional configuration, a gNB222 may also be connected to the NGC 260 via control plane interface 265to AMF/UPF 264 and user plane interface 263 to SMF 262. Further, eNB 224may directly communicate with gNB 222 via the backhaul connection 223,with or without gNB direct connectivity to the NGC 260. In someconfigurations, the New RAN 220 may only have one or more gNBs 222,while other configurations include one or more of both eNBs 224 and gNBs222. Either gNB 222 or eNB 224 may communicate with UEs 204 (e.g., anyof the UEs depicted in FIG. 1). The base stations of the New RAN 220communicate with the AMF-side of the AMF/UPF 264 over the N2 interfaceand the UPF-side of the AMF/UPF 264 over the N3 interface.

The functions of the AMF include registration management, connectionmanagement, reachability management, mobility management, lawfulinterception, transport for session management (SM) messages between theUE 204 and the SMF 262, transparent proxy services for routing SMmessages, access authentication and access authorization, transport forshort message service (SMS) messages between the UE 204 and the shortmessage service function (SMSF) (not shown), and security anchorfunctionality (SEAF). The AMF also interacts with the authenticationserver function (AUSF) (not shown) and the UE 204, and receives theintermediate key that was established as a result of the UE 204authentication process. In the case of authentication based on a UMTS(universal mobile telecommunications system) subscriber identity module(USIM), the AMF retrieves the security material from the AUSF. Thefunctions of the AMF also include security context management (SCM). TheSCM receives a key from the SEAF that it uses to derive access-networkspecific keys. The functionality of the AMF also includes locationservices management for regulatory services, transport for locationservices messages between the UE 204 and the location managementfunction (LMF) 270, as well as between the New RAN 220 and the LMF 270,evolved packet system (EPS) bearer identifier allocation forinterworking with the EPS, and UE 204 mobility event notification. Inaddition, the AMF also supports functionalities for non-3GPP accessnetworks.

Functions of the UPF include acting as an anchor point forintra-/inter-RAT mobility (when applicable), acting as an externalprotocol data unit (PDU) session point of interconnect to the datanetwork (not shown), providing packet routing and forwarding, packetinspection, user plane policy rule enforcement (e.g., gating,redirection, traffic steering), lawful interception (user planecollection), traffic usage reporting, quality of service (QoS) handlingfor the user plane (e.g., UL/DL rate enforcement, reflective QoS markingin the DL), UL traffic verification (service data flow (SDF) to QoS flowmapping), transport level packet marking in the UL and DL, DL packetbuffering and DL data notification triggering, and sending andforwarding of one or more “end markers” to the source RAN node.

The functions of the SMF 262 include session management, UE Internetprotocol (IP) address allocation and management, selection and controlof user plane functions, configuration of traffic steering at the UPF toroute traffic to the proper destination, control of part of policyenforcement and QoS, and downlink data notification. The interface overwhich the SMF 262 communicates with the AMF-side of the AMF/UPF 264 isreferred to as the N11 interface.

Another optional aspect may include a LMF 270, which may be incommunication with the NGC 260 to provide location assistance for UEs204. The LMF 270 can be implemented as a plurality of separate servers(e.g., physically separate servers, different software modules on asingle server, different software modules spread across multiplephysical servers, etc.), or alternately may each correspond to a singleserver. The LMF 270 can be configured to support one or more locationservices for UEs 204 that can connect to the LMF 270 via the corenetwork, NGC 260, and/or via the Internet (not illustrated).

FIG. 3 illustrates an exemplary architecture of a wireless device 300having a transceiver 306 capable of implementing carrier aggregation,according to aspects of the disclosure. The wireless device may be a UE,such as UE 204, or a base station, such as any of the base stationsdescribed herein. The transceiver 306 may be coupled to first and secondantennas 302 and 304.

The transceiver 306 includes receiver circuitry 340 and transmittercircuitry 350. The receiver circuitry 340 is capable of implementingcarrier aggregation. As such, in the example of FIG. 3, the receivercircuitry 340 includes two radios 310 and 322 coupled to the twoantennas 302 and 304, respectively. Note that although FIG. 3illustrates only two antennas 302 and 304 and two radios 310 and 322, aswill be appreciated, there may be more than two antennas and two radios.The transmitter circuitry 350 may also be capable of implementingcarrier aggregation similarly to the receiver circuitry 340, but this isnot shown in FIG. 3 for the sake of simplicity.

A transceiver (e.g., transceiver 306) generally includes a modem (e.g.,modem 334) and a radio (e.g., radio 310 or 322). The radio, broadlyspeaking, handles selection and conversion of the RF signals into thebaseband or intermediate frequency and converts the RF signals to thedigital domain. The modem is the remainder of the transceiver.

Referring to FIG. 3, radio 310 includes an amplifier 312, a mixer 314(also referred to as a signal multiplier) for signal down conversion, afrequency synthesizer 316 (also referred to as an oscillator) thatprovides signals to the mixer 314, a baseband filter (BBF) 318, and ananalog-to-digital converter (ADC) 320. Similarly, radio 322 includes anamplifier 324, a mixer 326, a frequency synthesizer 328, a BBF 330, andan ADC 332. The ADCs 320 and 332 are coupled to the signalcombiner/signal selector 336 of the modem 334, which is coupled to thedemodulator 338 of the modem 334. The demodulator 338 is coupled to apacket processor 342. The demodulator 338 and the packet processor 342provide demodulated and processed single or multiple output signals tothe communication controller and/or processing system 360.

Note that not every component illustrated in FIG. 3 is required for theoperation of the system. For example, in direct RF to basebandconversion receivers, or any other direct conversion receivers,including certain software defined radio (SDR) implementations, variouscomponents of the receiver circuitry 340 are not necessary, as is knownin the art. In addition, while FIG. 3 illustrates a single modem 334coupled to two radios 310 and 322, as will be appreciated, each radio310 and 322 may be coupled to a different modem, and the receivercircuitry 340 would therefore include the same number of radios andmodems.

As noted above, carrier aggregation is a technique whereby a wirelessdevice (e.g., wireless device 300) can receive and/or transmit onmultiple carrier frequencies at the same time, thereby increasingdownlink and uplink data rates. Thus, the wireless device 300 maysimultaneously utilize radio 310 to tune to one carrier frequency (e.g.,the anchor carrier) and radio 322 to tune to a different carrierfrequency (e.g., a secondary carrier). In addition, each radio 310 and322 may be tunable to a plurality of different frequencies, one at atime. The frequencies may be in different frequency “bands,” such asfrequencies in FR1, which include sub-6 GHz frequency bands, and/or FR2,which include frequency bands in the mmWave range (e.g., 30 to 300 GHz).

The wireless device 300 further includes a processing system 360 thatmay direct operations of its respective systems. Additionally, a memorycomponent 370 can provide storage for program codes and data used by theprocessing system 360 and/or the transceiver 306. For example, thememory component 370 may include instructions that, when executed by theprocessing system 360 and/or transceiver 306, cause the wireless device300 to perform the operations described herein. In an aspect, theprocessing system 360 may be an ASIC, or other processor,microprocessor, logic circuit, or other data processing device. In anaspect, the memory component 370 may be random access memory (RAM),flash memory, read-only memory (ROM), erasable programmable ROM (EPROM),electrically erasable programmable ROM (EEPROM), registers, hard disk, aremovable disk, or any other form of storage medium known in the art.

FIG. 4 illustrates an exemplary wireless communications system 400according to various aspects of the disclosure. In the example of FIG.4, a UE 204 is attempting to calculate an estimate of its position, orassist another entity (e.g., a base station or core network component,another UE, a location server, a third party application, etc.) tocalculate an estimate of its position. The UE 204 may communicatewirelessly with a plurality of base stations 402 a-d (collectively, basestations 402), which may correspond to any combination of base stations102 and 180 and/or WLAN AP 150 in FIG. 1, using RF signals andstandardized protocols for the modulation of the RF signals and theexchange of information packets. Note that while FIG. 4 illustrates oneUE 204 and four base stations 402, as will be appreciated, there may bemore UEs 204 and more or fewer base stations 402.

FIG. 4 further illustrates an aspect in which base stations 402 a and402 b form a DAS/RRH 420. For example, the base station 402 a may be theserving base station of the UE 204 and the base station 402 b may be aneighbor base station of the UE 204. As such, the base station 402 b maybe the RRH of the base station 402 a. The base stations 402 a and 402 bmay communicate with each other over a wired or wireless link 422.

To support position estimates, the base stations 402 may be configuredto broadcast reference RF signals (e.g., positioning reference signals(PRS), navigation reference signals (NRS), tracking reference signals(TRS), cell-specific reference signals (CRS), channel state informationreference signals (CSI-RS), demodulation reference signals (DMRS),synchronization signals, etc.) to UEs 204 in their coverage area toenable a UE 204 to measure reference RF signal timing differences (e.g.,observed time difference of arrival (OTDOA) or reference signal timedifference (RSTD)) between pairs of network nodes and/or to identify theline of sight (LOS) or shortest radio path between the UE 204 and thetransmitting base stations 402. Identifying the LOS/shortest path is ofinterest not only because that path can subsequently be used for OTDOAmeasurements between a pair of base stations 402, but also becauseidentifying the shortest path can directly provide some positioninginformation based on the direction of the path. Moreover, identificationof the shortest path can be used for other position estimation methodsthat require precise ToA estimation, such as round-trip-time (RTT)-basedmethods.

As noted above, 5G supports operation at very high and evenextremely-high frequency (EHF) bands, such as mmW frequency bands. Oneof the challenges for wireless communication at very high or extremelyhigh frequencies, however, is that a significant propagation loss mayoccur due to the high frequency. As the frequency increases, thewavelength may decrease, and the propagation loss may increase as well.At mmW frequency bands, the propagation loss may be severe. For example,the propagation loss may be on the order of 22 to 27 dB, relative tothat observed in either the 2.4 GHz or 5 GHz bands.

Propagation loss is also an issue in MIMO and massive MIMO systems inany band. The term MIMO as used herein generally refers to both MIMO andmassive MIMO. MIMO is a method for multiplying the capacity of a radiolink by using multiple transmit and receive antennas to exploitmultipath propagation. Multipath propagation occurs because RF signalsnot only travel by the shortest path between the transmitter andreceiver, which may be a LOS path, but also over a number of other pathsas they spread out from the transmitter and reflect off other objectssuch as hills, buildings, water, and the like on their way to thereceiver. A transmitter in a MIMO system includes multiple antennas andtakes advantage of multipath propagation by directing these antennas toeach transmit the same RF signals on the same radio channel to areceiver. The receiver is also equipped with multiple antennas tuned tothe radio channel that can detect the RF signals sent by thetransmitter. As the RF signals arrive at the receiver (some RF signalsmay be delayed due to the multipath propagation), the receiver cancombine them into a single RF signal. Because the transmitter sends eachRF signal at a lower power level than it would send a single RF signal,propagation loss is also an issue in a MIMO system.

To accurately determine the position of a UE 204 using the RTTprocedures described above with reference to FIGS. 5-6B, the UE 204needs to measure the reference RF signals received over the LOS path (orthe shortest NLOS path where an LOS path is not available), between theUE 204 and a network node (e.g., a base station 402, an antenna orantenna array of a base station 402). However, as discussed above, RFsignals travel not only by the LOS/shortest path between the transmitterand receiver, but also over a number of other paths (multipaths) as theRF signals spread out from the transmitter and reflect off other objectssuch as hills, buildings, water, and the like on their way to thereceiver. Thus, FIG. 4 illustrates a number of LOS paths 410 and anumber of NLOS paths 412 between the base stations 402 and the UE 704.

Specifically, FIG. 4 illustrates base station 402 a transmitting over anLOS path 410 a and an NLOS path 412 a, base station 402 b transmittingover an LOS path 410 b and two NLOS paths 412 b, base station 402 ctransmitting over an LOS path 410 c and an NLOS path 412 c, and basestation 402 d transmitting over an LOS path 410 d and an NLOS path 412d. As illustrated in FIG. 4, each NLOS path 412 reflects off some object430 (e.g., a building). As will be appreciated, each LOS path 410 andNLOS path 412 transmitted by a base station 402 may be transmitted bydifferent antennas of the base station 402 (e.g., as in a MIMO system),or may be transmitted by the same antenna of a base station 402 (therebyillustrating the propagation of an RF signal). Further, as used herein,the term “LOS path” or “shortest path” between a transmitter andreceiver refers to the straight line path from the transmitter to thereceiver. However, such a path may not be an actual LOS path (due toblockages). In that case, the next available path is an NLOS path, whichreflects off of some surface(s) when travelling from the transmitter tothe receiver.

A major bottleneck in determining the ToA measurements for the LOS pathis separating the measurement of the LOS path from measurements of theNLOS paths. It has been observed that distinctly different frequencybands have different propagation (and reflection) characteristics. Forexample, lower frequency bands (e.g., sub-6 Ghz) penetrate concrete andglass, while higher frequency bands (e.g., mmWave) reflect off of suchsurfaces. However, all frequency bands travel at the speed-of-light.Thus, the propagation delay for the LOS path is the same across everyfrequency band.

For example, referring back to FIG. 4, assume that base station 402 dtransmits a first reference signal on a high frequency band (e.g., ammWave frequency band) and a second reference signal on a low frequencyband (e.g., a sub-6 GHz frequency band). The first reference signal,carried on the high frequency band, follows a NLOS path 412 d,reflecting off of multiple objects 430, while the second referencesignal, carried on the low frequency band, follows a LOS path 410 dthough an object 430. As such, the second reference signal will arriveat the UE 204 before the first reference signal, having followed the LOSpath from the base station 402 d to the UE 204.

As another example, assume that base station 402 c also transmits afirst reference signal on a high frequency band (e.g., a mmWavefrequency band) and a second reference signal on a low frequency band(e.g., a sub-6 GHz frequency band). In this case, the first referencesignal, carried on the high frequency band, follows an LOS path 410 cdirectly to the UE 204, while the second reference signal, carried onthe low frequency band, follows an NLOS path 412 c. Specifically, inthis example, the second reference signal is partially reflected off ofan object 430 (the portion of the signal penetrating the object 430 isnot shown). As such, the second reference signal will arrive at the UE204 after the first reference signal, having followed the NLOS path fromthe base station 402 d to the UE 204.

This observation can be leveraged to discriminate between the LOS andNLOS path from a transmitter to a receiver, and therefore provideimproved positioning performance (e.g., speed, accuracy, etc.). Forexample, a receiver capable of carrier aggregation (e.g., UE 204) canreceive a reference RF signal from a transmitter (e.g., a base stationor TRP) on a higher frequency and a second reference RF signal from thetransmitter on a lower frequency, compare the ToAs of the receivedreference signals, and based on characteristics of the receivedreference signals (e.g., ToA, frequency, signal strength), determinewhich reference signal likely followed the LOS path between thetransmitter and the receiver. The receiver can then use the ToA of thatreference signal for positioning operations.

In an aspect, one radio (e.g., radio 310) of the receiver would be tunedto one frequency (e.g., the high frequency), and the other radio (e.g.,radio 322) would be tuned to the other frequency (e.g., the lowfrequency). To compare the ToA of the reference signals received by thetwo radios, the radios should be synchronized to the same time (e.g.,have aligned frame boundaries), or the relative offset between theradios should be known and the ToAs adjusted accordingly. Similarly, onthe transmission side, the reference signals may be transmitted at thesame time or may be transmitted with a known offset that can be used toadjust the ToA accordingly.

FIG. 5 illustrates an example of timing differences between LOS and NLOSpaths, according to aspects of the disclosure. Frame sequences 520 and522 illustrate the LOS case, where both the high frequency band (HB)reference signal and the low frequency band (LB) reference signal followthe LOS path between the transmitter (e.g., a base station 402) and thereceiver (e.g., a UE 204), arriving at the receiver at the same time,and thereby having the same ToA.

Frame sequences 530 and 532 illustrate the NLOS case. In frame sequence530, the high frequency band (HB) reference signal follows a NLOS pathfrom the transmitter (e.g., a base station 402) to the receiver (e.g., aUE 204), arriving at the receiver after the start of the frame. Incontrast, the low frequency band (LB) reference signal follows the LOSpath between the transmitter (e.g., a base station 402) and the receiver(e.g., a UE 204), arriving at the receiver at the start of the frame.(Note that in the example of FIG. 5, the receiver sets the start of itsframe time to the ToA of the LOS reference signal; however, this is notrequired.)

Generally, if the ToA of the high band reference signal is the same asthe ToA for the low band reference signal, then the measured ToA has ahigh probability of being the ToA of the LOS path. In some situations,however, a strong reflection of the reference signal on both bands maybe the only path detected at the receiver. Since both reference signalswill have the same ToA, because they will both have followed the sameNLOS path, this situation resembles the situation where they followed atruly LOS path in terms of the ToAs observed. This can be addressed byobserving the signal strength of the received reference signals, asdiscussed further below.

Typically, because a low band reference signal can penetrate obstaclesbetter than a high band reference signal, and is therefore more likelyto follow the shortest path from the transmitter to the receiver, theToA of the low band reference signal will often be earlier than, or atleast the same as, the ToA of the high band reference signal. Thus, ifthe ToA of the high band reference signal is later than the ToA of thelow band reference signal, the high band reference signal can beconsidered to have followed a NLOS path and be discarded for subsequentpositioning operations. Note that in this case, although the low bandreference signal may have followed a shorter path than the high bandreference signal, it may or may not have followed a LOS path.

In an aspect, the reference signal received power (RSRP), referencesignal received quality (RSRQ), and/or packet data protocol (PDP)measurements of the reference signals on both bands can provide furtherdetails for weighting the observations. For example, if the true LOSpath is blocked and the receiver is only receiving reflections of thereference signals, then the high band and low band reference signalscould have very different signal strengths, even though arriving at thesame time. Specifically, since high band frequencies are more robust toreflections than low band frequencies, the high band reference signalwill likely have a higher signal strength than the low band referencesignal, as the majority of the low band reference signal's energy willhave been absorbed by, or refracted at, the obstacle. Alternatively, ifthe true LOS path is not blocked but penetrates through an obstacle,then the high band will be attenuated more than the low band, andtherefore the low band reference signal will likely have a higher signalstrength than the high band reference signal. In either case, someknowledge of the transmit power or expected received signal strengthwould be beneficial, so that the receiver can compare the observedreceived signal strength to the expected signal strength. Thisinformation can be provided by the transmitter or observed over time bythe receiver.

The techniques described above for distinguishing between the LOS andNLOS path from a transmitter to a receiver can be used to improvepositioning performance (e.g., speed, accuracy, etc.). For example, forRTT procedures, the RTT between the transmitter and receiver may bemeasured separately on both frequency bands. That is, the receiverperforms a first RTT procedure with the transmitter over the highfrequency band and a second RTT procedure with the transmitter over thelow frequency band. In an aspect, the receiver may perform the RTTprocedures over the separate frequencies using different radios (e.g.,using radio 310 and radio 322), or using the same radio but switchingback and forth between the frequencies. In the former case, the separateradios should be synchronized to the same time, and in the latter case,that the receiver remains stationary during the consecutive RTTprocedures. In both cases, the transmitter and receiver should betime-synchronized (e.g., their respective frame times should bealigned).

Once measured on both frequency bands, the receiver (or another networkentity determining the location of the receiver, such as the servingbase station or location server) can compare the propagation time(T_(Prop)) between the transmitter and the receiver for each frequencyband. If the RTT for the high frequency band is the same as the RTT forthe low frequency band, then the RTT path has a high probability ofbeing a LOS path, the same as when the reference signals transmitted onthe high and low frequency bands have the same ToA at the receiver. ThatRTT can then be used to determine the position of the receiver.

As noted above, if the RTT of the high frequency band is the same as theRTT for the low frequency band, then the measured RTT has a highprobability of being the RTT of the LOS path. In some situations,however, a strong reflection of the reference signals on both bands maybe the only path detected at the receiver. Since both RTTs will have thesame length, because they will both have followed the same NLOS path,the receiver will think that they followed the LOS path. This can beaddressed by observing the signal strength of the received referencesignals, as discussed further below.

As noted above, low band reference signals penetrate obstacles betterthan high band reference signals, and are therefore more likely tofollow the shortest path from the transmitter to the receiver. As such,the RTT of the low frequency band will often be less than, or at leastthe same as, the RTT of the high frequency band. Thus, if the RTT of thehigh frequency band is longer than the RTT of the low frequency band,the high frequency band RTT can be considered to have followed a NLOSpath and be discarded for subsequent positioning operations. Note thatin this case, although the low frequency band RTT may have followed ashorter path than the high frequency band RTT, it may or may not havefollowed a LOS path.

In an aspect, the RSRP, RSRQ, and/or PDP measurements of the referencesignals used for the RTT procedures on the high and low frequency bandscan provide further details for weighting the observations. For example,as discussed above, if the true LOS path is blocked and the receiver isonly receiving reflections of the reference signals, then the high bandand low band reference signals could have very different signalstrengths, even though arriving at the same time. Specifically, sincehigh band frequencies are more robust to reflections than low bandfrequencies, the high band reference signals will likely have a highersignal strength than the low band reference signals, as the majority ofthe low band reference signals' energy will have been absorbed by theobstacle. In this case, some knowledge of the transmit power or expectedreceived signal strength would be beneficial, so that the receiver cancompare the observed received signal strength to the expected signalstrength. This information can be provided by the transmitter orobserved over time by the receiver.

FIG. 6 illustrates an example of differences between LOS and NLOS RTTs,according to aspects of the disclosure. Example scenario 600A representsthe LOS case, in which the high frequency band RTT and the low frequencyband RTT between the transmitter (e.g., a base station or TRP) and thereceiver (e.g., a UE 204) are the same, as illustrated by the equallength RTT lines. In contrast, in example scenario 600B, which is anNLOS case, the high frequency band RTT is longer than the low frequencyband RTT, indicating that the high frequency band RTT followed an NLOSpath. In that case, the high frequency band RTT would be discarded andthe low frequency band RTT would be used to determine the position ofthe receiver.

The techniques described herein raise various implications for networksignaling. For example, on the network side, frequency carriers (or thereference signals on the component carriers) should be tightly timesynchronized for purposes of OTDOA positioning (where the receivermeasures timing differences between pairs of network nodes). Ideally,the leading edge of a frame would have no offset (or a fixed offset withhigh precision) between network nodes. For RTT procedures, the carriersshould be calibrated to equal precision. For uplink time difference ofarrival (UTDOA), the carriers should be tightly synchronized at the UE.

Regarding UE reporting requirements, OTDOA reports on both frequencybands would be assumed to have been measured with respect to the sameclock (i.e., fully time synchronized). Thus, the OTDOA may be withrespect to a reference signal on one of the frequency bands, representedas, for example,OTDOA_(cellID,bandID)=TOA_(cellID,bandID)−TOA_(cell0,band0),Where“cell0” is the reference cell and “band0” is the reference frequencyband. For RTT, the receiver, if not calculating its own position, shouldreport the RTT across both bands. That is, the receiver reports theRx-to-Tx per band, but may report both on a single band, for example,the low band. The reference signal in the RTT response is still neededin both bands. For UTDOA, the uplink reference signal for UTDOA acrossthe frequency bands may have an associated Tx-to-Tx offset report.

Regarding the receiver (e.g., UE 204) capabilities needed, the ToAreports for both frequency bands should be associated with the sameclock (or with some limit on timing accuracy between frequency bands)for OTDOA. In addition, the reference signals for UTDOA should havetight synchronization (or support an accurate report of any offsets).

Note that although the foregoing has generally referred to the receiveras a UE and the transmitter as a base station or TRP, the receiver mayalternatively be a base station or TRP and the transmitter mayalternatively be a UE, or both the receiver and transmitter may be basestations or TRPs, or both the receiver and transmitter may be UEs.

FIG. 7 illustrates a method 700 of determining an LOS path between atransmitter (e.g., a UE 204, a base station, a TRP) and a wirelessdevice (e.g., another UE 204, a base station, a TRP) in a wirelesscommunications network, according to aspects of the disclosure. Themethod 700 may be performed by the wireless device.

At 710, the wireless device receives a first reference signal (e.g.,PRS, NRS, TRS, CRS, DMRS, CSI-RS, etc.) on a first frequency band (e.g.,a high frequency band in FR2) at a first time (e.g., a first ToA). In anaspect, operation 710 may be performed by antenna 302, receivercircuitry 340 (e.g., radio 310), processing system 360, and/or memorycomponent 370, any or all of which may be considered means forperforming this operation.

At 720, the wireless device receives a second reference signal on asecond frequency band (e.g., a low frequency band in FR1) at a secondtime (e.g., a second ToA). In an aspect, operation 720 may be performedby antenna 304, receiver circuitry 340 (e.g., radio 322), processingsystem 360, and/or memory component 370, any or all of which may beconsidered means for performing this operation.

At 730, the wireless device compares the first time to the second time.In an aspect, operation 730 may be performed by modem 334, processingsystem 360, and/or memory component 370, any or all of which may beconsidered means for performing this operation.

At 740, the wireless device determines, at least based on the comparisonof the first time to the second time, which of the first referencesignal and/or the second reference signal followed the LOS path betweenthe transmitter and the wireless device. In an aspect, operation 740 maybe performed by modem 334, processing system 360, and/or memorycomponent 370, any or all of which may be considered means forperforming this operation.

At 750, the wireless device optionally reports, to a positioning entity(e.g., the serving base station or a location server) the transmitter,which of the first reference signal and/or the second reference signalfollowed the LOS path. Alternatively, the wireless device optionallyreports, to the transmitter, a difference between the first time and thesecond time, a signal strength of the first reference signal, and asignal strength of the second reference signal. As yet anotheralternative, the wireless device optionally reports, to the transmitter,the first time, the second time, a signal strength of the firstreference signal, and a signal strength of the second reference signal.In an aspect, operation 750 may be performed by antenna 302 or 304,transmitter circuitry 350, processing system 360, and/or memorycomponent 370, any or all of which may be considered means forperforming this operation.

Additionally, the method 700 may include (not shown) the wireless deviceestimating its own location based on a ToA of whichever of the firstreference signal and/or the second reference signal followed the LOSpath. For example, the wireless device may use the ToA to calculate theRTT between itself and the transmitter, and from the RTT, an estimate ofthe location of the wireless device (e.g., using RTTs between thewireless device and other transmitters or just the one RTT and angle ofarrival (AoA) or angle of departure (AoD) information). Alternatively,the wireless device may report such measurements to a positioningentity, and the positioning entity may calculate the location of thewireless device.

Those of skill in the art will appreciate that information and signalsmay be represented using any of a variety of different technologies andtechniques. For example, data, instructions, commands, information,signals, bits, symbols, and chips that may be referenced throughout theabove description may be represented by voltages, currents,electromagnetic waves, magnetic fields or particles, optical fields orparticles, or any combination thereof.

Further, those of skill in the art will appreciate that the variousillustrative logical blocks, modules, circuits, and algorithm stepsdescribed in connection with the aspects disclosed herein may beimplemented as electronic hardware, computer software, or combinationsof both. To clearly illustrate this interchangeability of hardware andsoftware, various illustrative components, blocks, modules, circuits,and steps have been described above generally in terms of theirfunctionality. Whether such functionality is implemented as hardware orsoftware depends upon the particular application and design constraintsimposed on the overall system. Skilled artisans may implement thedescribed functionality in varying ways for each particular application,but such implementation decisions should not be interpreted as causing adeparture from the scope of the present disclosure.

The various illustrative logical blocks, modules, and circuits describedin connection with the aspects disclosed herein may be implemented orperformed with a general purpose processor, a DSP, an ASIC, an FPGA, orother programmable logic device, discrete gate or transistor logic,discrete hardware components, or any combination thereof designed toperform the functions described herein. A general purpose processor maybe a microprocessor, but in the alternative, the processor may be anyconventional processor, controller, microcontroller, or state machine. Aprocessor may also be implemented as a combination of computing devices,e.g., a combination of a DSP and a microprocessor, a plurality ofmicroprocessors, one or more microprocessors in conjunction with a DSPcore, or any other such configuration.

The methods, sequences and/or algorithms described in connection withthe aspects disclosed herein may be embodied directly in hardware, in asoftware module executed by a processor, or in a combination of the two.A software module may reside in RAM, flash memory, ROM, EPROM, EEPROM,registers, hard disk, a removable disk, a CD-ROM, or any other form ofstorage medium known in the art. An exemplary storage medium is coupledto the processor such that the processor can read information from, andwrite information to, the storage medium. In the alternative, thestorage medium may be integral to the processor. The processor and thestorage medium may reside in an ASIC. The ASIC may reside in a userterminal (e.g., UE). In the alternative, the processor and the storagemedium may reside as discrete components in a user terminal.

In one or more exemplary aspects, the functions described may beimplemented in hardware, software, firmware, or any combination thereof.If implemented in software, the functions may be stored on ortransmitted over as one or more instructions or code on acomputer-readable medium. Computer-readable media includes both computerstorage media and communication media including any medium thatfacilitates transfer of a computer program from one place to another. Astorage media may be any available media that can be accessed by acomputer. By way of example, and not limitation, such computer-readablemedia can comprise RAM, ROM, EEPROM, CD-ROM or other optical diskstorage, magnetic disk storage or other magnetic storage devices, or anyother medium that can be used to carry or store desired program code inthe form of instructions or data structures and that can be accessed bya computer. Also, any connection is properly termed a computer-readablemedium. For example, if the software is transmitted from a website,server, or other remote source using a coaxial cable, fiber optic cable,twisted pair, digital subscriber line (DSL), or wireless technologiessuch as infrared, radio, and microwave, then the coaxial cable, fiberoptic cable, twisted pair, DSL, or wireless technologies such asinfrared, radio, and microwave are included in the definition of medium.Disk and disc, as used herein, includes compact disc (CD), laser disc,optical disc, digital versatile disc (DVD), floppy disk and Blu-ray discwhere disks usually reproduce data magnetically, while discs reproducedata optically with lasers. Combinations of the above should also beincluded within the scope of computer-readable media.

While the foregoing disclosure shows illustrative aspects of thedisclosure, it should be noted that various changes and modificationscould be made herein without departing from the scope of the disclosureas defined by the appended claims. The functions, steps and/or actionsof the method claims in accordance with the aspects of the disclosuredescribed herein need not be performed in any particular order.Furthermore, although elements of the disclosure may be described orclaimed in the singular, the plural is contemplated unless limitation tothe singular is explicitly stated.

What is claimed is:
 1. A method at a wireless device of determining aline-of-sight (LOS) path between a transmitter and the wireless device,comprising: receiving, from the transmitter, a first reference signal ona first frequency band at a first time; receiving, from the transmitter,a second reference signal on a second frequency band at a second time;comparing the first time to the second time; and determining, at leastbased on the comparing the first time to the second time, which of thefirst reference signal and/or the second reference signal followed theLOS path between the transmitter and the wireless device.
 2. The methodof claim 1, further comprising: tuning, by a first radio of the wirelessdevice, to the first frequency band to receive the first referencesignal; and tuning, by a second radio of the wireless device, to thesecond frequency band to receive the second reference signal.
 3. Themethod of claim 2, wherein the first radio and the second radio aresynchronized in time with each other.
 4. The method of claim 3, whereinthe first radio and the second radio are synchronized in time with thetransmitter.
 5. The method of claim 1, further comprising: tuning, by aradio of the wireless device, to the first frequency band to receive thefirst reference signal; and tuning, by the radio of the wireless device,to the second frequency band to receive the second reference signal. 6.The method of claim 1, wherein the first frequency band comprises a highfrequency band and the second frequency band comprises a low frequencyband.
 7. The method of claim 6, wherein the first time is after thesecond time.
 8. The method of claim 7, further comprising: determining,based on the first time being after the second time, that the firstreference signal did not follow the LOS path.
 9. The method of claim 7,further comprising: determining, based on the first time being after thesecond time and a signal strength of the second reference signal beingabove a threshold, that the second reference signal followed the LOSpath.
 10. The method of claim 7, further comprising: determining, basedon the first time being after the second time and a signal strength ofthe second reference signal being below a threshold, that both the firstreference signal and the second reference signal did not follow the LOSpath.
 11. The method of claim 6, wherein the first time is the same asthe second time.
 12. The method of claim 11, further comprising:determining, based on the first time being the same as the second time,that both the first reference signal and the second reference signalfollowed the LOS path.
 13. The method of claim 11, further comprising:determining, based on the first time being the same as the second timeand a signal strength of the second reference signal being higher than asignal strength of the first reference signal, that both the firstreference signal and the second reference signal followed the LOS paththrough an obstacle.
 14. The method of claim 11, further comprising:determining, based on the first time being the same as the second timeand a signal strength of the second reference signal being below athreshold, that both the first reference signal and the second referencesignal did not follow the LOS path.
 15. The method of claim 1, furthercomprising: reporting, to the transmitter, which of the first referencesignal and/or the second reference signal followed the LOS path.
 16. Themethod of claim 15, wherein a time of arrival of whichever of the firstreference signal and/or the second reference signal followed the LOSpath is used by a positioning entity in a round-trip-time positioningprocedure.
 17. The method of claim 1, further comprising: estimating alocation of the wireless device based on a time of arrival of whicheverof the first reference signal and/or the second reference signalfollowed the LOS path.
 18. The method of claim 1, further comprising:reporting, to the transmitter, the first time, the second time, a signalstrength of the first reference signal, and a signal strength of thesecond reference signal.
 19. The method of claim 1, further comprising:reporting, to the transmitter, a difference between the first time andthe second time, a signal strength of the first reference signal, and asignal strength of the second reference signal.
 20. The method of claim1, further comprising: sending, to the transmitter, an indication thatthe wireless device is capable of measuring a time of arrival of areference signal on multiple frequency bands within a given accuracy.21. The method of claim 1, wherein: the wireless device comprises a userequipment and the transmitter comprises a base station ortransmission-reception point (TRP), the wireless device comprises afirst base station or TRP and the transmitter comprises a second basestation or TRP, the wireless device comprises a base station or TRP andthe transmitter comprises a user equipment, or the wireless devicecomprises a user equipment and the transmitter comprises a userequipment.
 22. The method of claim 1, wherein the first and secondreference signals are transmitted at the same time or with a knownoffset that can be used to adjust the first time and the second time.23. The method of claim 22, further comprising: receiving an indicationof the known offset from the transmitter.
 24. A wireless device,comprising: a memory; at least one transceiver; and at least oneprocessor, wherein the at least one processor is configured to: receive,from a transmitter via the at least one transceiver, a first referencesignal on a first frequency band at a first time; receive, from thetransmitter via the at least one transceiver, a second reference signalon a second frequency band at a second time; compare the first time tothe second time; and determine, at least based on the comparison of thefirst time to the second time, which of the first reference signaland/or the second reference signal followed a line of site (LOS) pathbetween the transmitter and the wireless device.
 25. The wireless deviceof claim 24, further comprising: a first radio of the at least onetransceiver configured to tune to the first frequency band to receivethe first reference signal; and a second radio of the at least onetransceiver configured to tune to the second frequency band to receivethe second reference signal.
 26. The wireless device of claim 25,wherein the first radio and the second radio are synchronized in timewith each other.
 27. The wireless device of claim 26, wherein the firstradio and the second radio are synchronized in time with thetransmitter.
 28. The wireless device of claim 24, further comprising: aradio of the at least one transceiver configured to tune to the firstfrequency band to receive the first reference signal, and configured totune to the second frequency band to receive the second referencesignal.
 29. The wireless device of claim 24, wherein the first frequencyband comprises a high frequency band and the second frequency bandcomprises a low frequency band.
 30. The wireless device of claim 29,wherein the first time is after the second time.
 31. The wireless deviceof claim 30, wherein, based on the first time being after the secondtime, the at least one processor is configured to determine that thefirst reference signal did not follow the LOS path.
 32. The wirelessdevice of claim 30, wherein, based on the first time being after thesecond time and a signal strength of the second reference signal beingabove a threshold, the at least one processor is configured to determinethat the second reference signal followed the LOS path.
 33. The wirelessdevice of claim 30, wherein, based on the first time being after thesecond time and a signal strength of the second reference signal beingbelow a threshold, the at least one processor is configured to determinethat both the first reference signal and the second reference signal didnot follow the LOS path.
 34. The wireless device of claim 29, whereinthe first time is the same as the second time.
 35. The wireless deviceof claim 34, wherein, based on the first time being the same as thesecond time, the at least one processor is configured to determine thatboth the first reference signal and the second reference signal followedthe LOS path.
 36. The wireless device of claim 34, wherein, based on thefirst time being the same as the second time and a signal strength ofthe second reference signal being higher than a signal strength of thefirst reference signal, the at least one processor is configured todetermine that both the first reference signal and the second referencesignal followed the LOS path through an obstacle.
 37. The wirelessdevice of claim 34, wherein, based on the first time being the same asthe second time and a signal strength of the second reference signalbeing below a threshold, the at least one processor is configured todetermine that both the first reference signal and the second referencesignal did not follow the LOS path.
 38. The wireless device of claim 24,wherein the at least one processor is further configured to: cause theat least one transceiver to report, to the transmitter, which of thefirst reference signal and/or the second reference signal followed theLOS path.
 39. The wireless device of claim 38, wherein a time of arrivalof whichever of the first reference signal and/or the second referencesignal followed the LOS path is used by a positioning entity in around-trip-time positioning procedure.
 40. The wireless device of claim24, wherein the at least one processor is further configured to:estimate a location of the wireless device based on a time of arrival ofwhichever of the first reference signal and/or the second referencesignal followed the LOS path.
 41. The wireless device of claim 24,wherein the at least one processor is further configured to: cause theat least one transceiver to report, to the transmitter, the first time,the second time, a signal strength of the first reference signal, and asignal strength of the second reference signal.
 42. The wireless deviceof claim 24, wherein the at least one processor is further configuredto: cause the at least one transceiver to report, to the transmitter, adifference between the first time and the second time, a signal strengthof the first reference signal, and a signal strength of the secondreference signal.
 43. The wireless device of claim 24, wherein the atleast one processor is further configured to: cause the at least onetransceiver to send, to the transmitter, an indication that the wirelessdevice is capable of measuring a time of arrival of a reference signalon multiple frequency bands within a given accuracy.
 44. The wirelessdevice of claim 24, wherein: the wireless device comprises a userequipment and the transmitter comprises a base station ortransmission-reception point (TRP), the wireless device comprises afirst base station or TRP and the transmitter comprises a second basestation or TRP, the wireless device comprises a base station or TRP andthe transmitter comprises a user equipment, or the wireless devicecomprises a user equipment and the transmitter comprises a userequipment.
 45. The wireless device of claim 24, wherein the first andsecond reference signals are transmitted at the same time or with aknown offset that can be used to adjust the first time and the secondtime.
 46. The wireless device of claim 24, wherein the at least oneprocessor is further configured to: receive, via the at least onetransceiver, an indication of the known offset from the transmitter. 47.A wireless device, comprising: means for receiving, from thetransmitter, a first reference signal on a first frequency band at afirst time; means for receiving, from the transmitter, a secondreference signal on a second frequency band at a second time; means forcomparing the first time to the second time; and means for determining,at least based on the comparison of the first time to the second time,which of the first reference signal and/or the second reference signalfollowed a line of site (LOS) path between the transmitter and thewireless device.
 48. A non-transitory computer-readable medium storingcomputer-executable instructions, the computer-executable instructionscomprising: at least one instruction instructing a wireless device toreceive, from the transmitter, a first reference signal on a firstfrequency band at a first time; at least one instruction instructing thewireless device to receive, from the transmitter, a second referencesignal on a second frequency band at a second time; at least oneinstruction instructing the wireless device to compare the first time tothe second time; and at least one instruction instructing the wirelessdevice to determine, at least based on the comparison of the first timeto the second time, which of the first reference signal and/or thesecond reference signal followed a line of site (LOS) path between thetransmitter and the wireless device.